Ecomorphology of Skates (Rajoidei): Connecting Variable Form to Feeding and Diet

Variation in feeding-related structures often affects the mode and mechanism of prey acquisition in many groups of organisms. Such diversity may therefore have direct consequences for ecological interactions within a system. We investigated the connection between morphology and diet in three co-occurring species of Northwest Atlantic skate.  Skates, fishes closely related to stingrays, notably vary in their rostral or snout morphology. Species with reduced rostrums are able to manipulate their anterior margins in a manner that disturbs sediments and unearths sediment-dwelling prey (e.g. polychaete worms, sand lance, etc.). However, those with elongated and highly calcified rostrums should not have the same rostral dexterity. Consequently, we predicted that skates with long rostrums feed less effectively on prey associated with the sediment and that this would be reflected in their dietary composition. To test this we first quantified and described shape differences among skate species that vary in rostral morphology using geometric morphometrics, a multivariate shape analysis tool.  We then used a two-block partial least-squares analysis to identify patterns of covariation between morphological variables and dietary composition for each species. Preliminary work confirms the existence of separate rostral morphotypes. Given the ubiquity of skates in the NW Atlantic, this research provides useful knowledge on a process (i.e. trophic interactions between skates and other species) that likely plays an important role in community dynamics.